Intratumoral injection of taxol in vivo suppresses A549 tumor showing cytoplasmic vacuolization

Abstract

Based on our recent in vitro studies, this report was designed to explore the mechanism by which high concentration of taxol (70 µM) induced paraptosis-like cell death in human lung carcinoma (A549) cells, and to evaluate the therapeutic efficacy of taxol using A549 tumor-bearing mice in vivo. Exposure of cells to taxol induced time-dependent cytotoxicity and cytoplasmic vacuolization without the involvement of Bax, Bak, Mcl-1, Bcl-XL, and caspase-3. Although taxol treatment induced activating transcription factor 6 (ATF6) cleavage indicative of endoplasmic reticulum (ER) stress, silencing ATF6 by shATF6 did not prevent taxol-induced both cytotoxcity and cytoplasmic vacuolization, suggesting that taxol-induced cytoplasmic vacuolization and cell death were not due to ER stress. Moreover, taxol-treated cells did not show DNA fragmentation and loss of mitochondrial membrane potential, the typical characteristics of apoptosis. In addition, taxol-induced cytoplasmic vacuolization did not show the cellular lysis, the characteristics of oncosis, and positive of β-galactosidase, the characteristic of senescence, indicating that taxol induced paraptosis-like cell death is neither oncosis nor senescence. Moreover, our in vivo data showed that intratumoral injection of taxol (50 mg/kg) in A549 tumor xenograft mice on day 1 and day 19 potently suppressed tumor growth showing significant ER vacuolization without toxicity. In conclusion, high concentration of taxol exhibits a significant anticancer activity by inducing paraptosis-like cell death in vitro and in vivo, without significant toxicity, suggesting a promising therapeutic strategy for apoptosis-resistance cancer by inducing ER vacuolization.

TAXOL INDUCES CELL DEATH WITH CYTOPLASM VACUOLIZATION IN PARAPTOSIS-LIKE BUT NOT ONCOSIS FASHION IN ASTC-a-1 CELLS

“…We referred to this cell death form as parapotis-like cell death according to the similarity in morphology. [12][13][14] We have demonstrated that the taxolinduced vacuolization is from ER and mitochondrial; we have further demonstrated that caspases and Bcl-XL do not participate in the taxol-induced cytoplasm vacuolization. However, we have not delineated the taxol-induced cell death as paraptosis-like cell death or oncosis previously.…”

“…EGFP was excited at 488 nm and°uorescence emission was recorded through a 500-550 nm band-pass¯lter. [12][13][14] In this study, 70 M of taxol was adopted in all experiments as described previously. 12,13 We used FCM analysis to assess the temporal relationship between the taxol-induced cytoplasm vacuolization and dissipation of ÁÉm.…”

“…4 Because the mitochondrial generation of ATP requires electrochemical gradient, a reduction in mitochondrial membrane potential may precede the morphologic changes observed in oncotic cell death. 11 We recently found that high concentration of taxol (70 M) induced cell death with cytoplasm vaculization in paraptosis-like fashion in HeLa, U87, A549 and ASTC-a-1 cell lines, [12][13][14] and low concentration of taxol (35 nM) induced cell death mainly in apoptotic fashion. 15 Cytoplasm vacuolization from endoplasmic reticulum (ER) and/or mitochondrial swelling together with absence of apoptotic DNA fragmentation and caspase activation are the characteristics of paraptosis.…”

Loco-regional administration of nanomedicines for the treatment of lung cancer

“…It is important to note that this altered ECM is a particular issue for nanoparticles due to the sheer size of the systems, particularly in comparison to free drug (Holback & Yeo, 2011). There has been a considerable amount of work done looking at intratumoral delivery of free anticancer drugs such as docetaxel (Yoo et al, 2010), cisplatin (Celikoglu et al, 2006a,b), and paclitaxel (Wang & Chen, 2012). Celikoglu group has produced some comprehensive reviews of the delivery of cytotoxic drugs by intratumoral injection, particularly via bronchoscopy and there appears to be a considerable opportunity to achieve even more in this treatment modality (Celikoglu et al, 2008(Celikoglu et al, , 2010.…”

Pharmacokinetics and safety of paclitaxel delivery into porcine airway walls by a new endobronchial drug delivery catheter

“…In an effort to further reduce tumour mass and improve outcomes of therapeutic bronchoscopy in patients with malignant airway obstruction, the intratumoral administration of chemotherapeutic agents has been proposed as an adjunctive therapy. In animal models and in patients with lung cancer, this approach has demonstrated successful results in delaying tumour recurrence . A new drug delivery catheter, the Blowfish Transbronchial Micro‐Infusion Catheter (Mercator MedSystems, Emeryville, CA, USA) was developed to directly deliver medication safely and reliably into the airway wall by way of a microneedle port.…”